Intestinal Injury and Endotoxemia in Children Undergoing Surgery for Congenital Heart Disease

Cardiopulmonary bypass with deep hypothermic circulatory arrest results in organ-specific transcriptomic responses in pediatric swine

The organ-level molecular response to cardiac surgery with cardiopulmonary bypass (CPB) remains inadequately understood and may be heterogeneous. Here, we measured organ-specific gene expression in a piglet model of CPB with deep hypothermic circulatory arrest (DHCA). Infant piglets underwent peripheral CPB with 75 min of DHCA and 6 h of critical care after separation from CPB. Mechanically ventilated animals served as controls. Tissue was obtained from the lung, kidney, liver, heart, and ileum. RNA sequencing was performed using NovaSeq 6000 and evaluated via differentially expressed gene (DEG) and pathway/network analyses. CPB/DHCA induced significant transcriptomic alterations, with greater changes seen in liver (2,166 DEGs), heart (775 DEGs), and kidney (1,759 DEGs) compared to lung (401 DEGs) and ileum (11 DEGs), and little overlap across organs (<20 % differentially expressed in >1 organ). Key upregulated systems included ribosomal proliferation and mitochondrial assembly in the liver, oxidative stress response and proximal tubular repair in the kidney, myofilament structural genes and pro-hypertrophy pathways in the heart, and solute channels and arginine metabolism in the lung. Downregulation of adaptive immunity genes occurred in multiple organs. Transcriptomics could inform the investigation of targeted therapies and adverse event screening after cardiac surgery.

Trajectory of gut microbiota before and after pediatric cardiopulmonary bypass surgery

Background

Varied congenital heart disease (CHD) may induce gut microbiota dysbiosis due to intestinal hypoperfusion or/and hypoxemia. Microbiota dysbiosis has been found in preoperative infants and cardiopulmonary bypass (CPB) exacerbated it further. However, the trajectory of gut microbiota from pre- to early post-CPB and one-year later remains unexplored. We examined this trajectory in the two most common CHDs, i.e., left-to-right shunt (ventricular septal defect, VSD) vs. right-to-left shunt (tetralogy of Fallot, TOF).

Methods

We enrolled 13 infants with VSD and 11 with TOF, and collected fecal samples at pre- and early post-CPB. 10 and 12 age- and gender-matched healthy control infants were enrolled respectively. We also enrolled 13 and 9 gender- and CHD diagnosis- and operation-matched one-year post-CPB patients, and 8 age- and gender-matched healthy control children. 16S rRNA sequencing of fecal samples were performed.

Results

Compared to the control groups, both VSD and TOF pre-CPB groups had significantly increased Enterobacteriaceae and Shigella, and decreased Bifidobacterium (Ps ≤ 0.049). No significant change in microbial community diversity was observed between pre- and early post-CPB periods (Ps≥0.227). Compared with early post-CPB, one-year post-CPB groups had significantly increased short-chain fatty acids-producing microbes (Ps ≤ 0.025), and their microbial communities were close to that of the control group (Ps≥0.102). There was no significant difference in microbial communities between VSD and TOF groups in any of 3 periods (Ps≥0.055).

Conclusion

In children with VSD or TOF, gut microbiota dysbiosis existed preoperatively and were not significantly altered by CPB. One-year post-CPB, microbiota significantly improved towards normal. Similar microbial communities were found between children with VSD and TOF throughout the perioperative and long-term postoperative periods.

Noninvasive Tools to Predict Necrotizing Enterocolitis in Infants with Congenital Heart Diseases: A Narrative Review

BACKGROUND

Necrotizing enterocolitis (NEC) is the most frightening gastrointestinal emergency in newborns. Despite being primarily a disease of premature infants, neonates with congenital heart disease (CHD) are at increased risk of development. Acute and chronic hemodynamic changes in this population may lead to mesenteric circulatory insufficiency.

OBJECTIVES

In this narrative review, we describe monitoring tools, alone or in multimodal use, that may help in the early recognition of patients with CHD at major risk of NEC development.

METHODS

We focused on vital parameters, echocardiography, Doppler flowmetry, abdominal near-infrared spectroscopy (aNIRS), and abdominal ultrasound (aUS).

RESULTS

The number of studies on this topic is small and includes a wide range of patients' ages and types of CHD. Peripheral oxygen saturation (SpO2) and certain echocardiographic indices (antegrade and retrograde velocity time integral, cardiac output, etc.) do not seem to differentiate infants with further onset of NEC from those not developing it. Hypotensive events, persistent diastolic flow reversal in the descending aorta, and low mesenteric oxygen saturation (rsSO2) measured by aNIRS appear to occur more frequently in infants who later develop NEC. aUS may be helpful in the diagnosis of cardiac NEC, potentially showing air contrast tracked to the right atrium in the presence of pneumatosis.

CONCLUSIONS

This narrative review describes the current knowledge on bedside tools for the early prediction of cardiac NEC. Future research needs to further explore the use of easy-to-learn, reproducible instruments to assist patient status and monitor patient trends.

Impact of postoperative necrotizing enterocolitis after neonatal cardiac surgery on neurodevelopmental outcome at 1 year of age

Objectives

We analyzed the impact of postoperative necrotizing enterocolitis (NEC) after cardiac surgery in neonatal age on neurodevelopmental (ND) outcome at 1 year of age.

Methods

Using data from the Swiss Neurodevelopmental Outcome Registry for Children with Congenital Heart Disease (ORCHID), we analyzed perioperative variables including postoperative NEC (Bell's stage ≥2) and 1-year ND outcome (Bayley III).

Results

The included patients (n = 101) had congenital heart disease (CHD), categorized as follows: 77 underwent biventricular repair for CHD with two functional chambers, 22 underwent staged palliation until the Fontan procedure for CHD with single ventricle physiology (n = 22), or 4 underwent single ventricle palliation or biventricular repair for borderline CHD (n = 4). Neonatal cardiopulmonary bypass (CBP) surgery was performed at a median age (IQR) of 8 (6) days. NEC occurred in 16 patients. Intensive care unit (ICU) length of stay (LOS) and the total duration of the hospitalization were longer in children with NEC than those in others (14 with vs. 8 days without NEC, p < 0.05; 49 with vs. 32 days without NEC, p < 0.05). The Bayley III scores of the analyzed patients determined at an age of 11.5 ± 1.5 months showed cognitive (CCS) (102.2 ± 15.0) and language scores (LCS) (93.8 ± 13.1) in the normal range and motor composite scores (MCS) (88.7 ± 15.9) in the low-normal range. After adjusting for socioeconomic status and CHD type, patients with NEC had lower CCS scores [β = -11.2 (SE 5.6), p = 0.049]. Using a cumulative risk score including NEC, we found a higher risk score to be associated with both lower CCS [β = -2.8 (SE 1.3), p = 0.030] and lower MCS [β = -3.20 (SE 1.3), p = 0.016].

Conclusions

Postoperative NEC is associated with longer ICU and hospital LOS and contributes together with other complications to impaired ND outcome at 1 year of age. In the future, national and international patient registries may provide the opportunity to analyze large cohorts and better identify the impact of modifiable perioperative risk factors on ND outcome.

Clinical Trial Registration

ClinicalTrials.gov identifier: NCT05996211.

Hypoxia exacerbates intestinal injury and inflammatory response mediated by myeloperoxidase during Salmonella Typhimurium infection in mice

BACKGROUND

High-altitude exposure can cause oxidative stress damage in the intestine, which leads to increased intestinal permeability and bacterial translocation, resulting in local and systemic inflammation. Control of infection is critically dependent on the host's ability to kill pathogens with reactive oxygen species (ROS). Myeloperoxidase (MPO) targets ROS in pathogens. This study aimed to investigate the effects of hypoxia on the colonic mucosal barrier and myeloperoxidase (MPO)-mediated innate immune response in the colon.

METHODS AND RESULTS

Genetically engineered mice were exposed to a hypobaric oxygen chamber for 3 days and an inflammation model was established using Salmonella Typhimurium infection. We found that hypoxic exposure caused the development of exacerbated bacterial colitis and enhanced bacterial dissemination in MPO-deficient mice. Infection and disease severity were associated with significantly increased Ly6G+ neutrophil and F4/80+ macrophage counts in infected tissues, which is consistent with elevated proinflammatory cytokines and chemoattractant molecules. Hypoxia restrained antioxidant ability and MPO deficiency aggravated the respiratory burst in the colon.

CONCLUSION

Hypoxia can damage the colonic mucosa. MPO mediates the innate immune response and regulates the mucosal and systemic inflammatory responses to Salmonella infection during hypoxia.

From heart to gut: Exploring the gut microbiome in congenital heart disease

Congenital heart disease (CHD) is a prevalent birth defect and a significant contributor to childhood mortality. The major characteristics of CHD include cardiovascular malformations and hemodynamical disorders. However, the impact of CHD extends beyond the circulatory system. Evidence has identified dysbiosis of the gut microbiome in patients with CHD. Chronic hypoxia and inflammation associated with CHD affect the gut microbiome, leading to alterations in its number, abundance, and composition. The gut microbiome, aside from providing essential nutrients, engages in direct interactions with the host immune system and indirect interactions via metabolites. The abnormal gut microbiome or its products can translocate into the bloodstream through an impaired gut barrier, leading to an inflammatory state. Metabolites of the gut microbiome, such as short-chain fatty acids and trimethylamine N-oxide, also play important roles in the development, treatment, and prognosis of CHD. This review discusses the role of the gut microbiome in immunity, gut barrier, neurodevelopment, and perioperative period in CHD. By fostering a better understanding of the cross-talk between CHD and the gut microbiome, this review aims to contribute to improve clinical management and outcomes for CHD patients.

Biomarkers and Functional Assays of Epithelial Barrier Disruption and Gastrointestinal Dysmotility in Critical Illness-A Narrative Review

Enteral nutrition in critically ill children has been associated with improved clinical outcomes. Gastrointestinal dysfunction often impedes the timely initiation and advancement of enteral nutrition and can contribute to immune dysregulation and systemic inflammation. Therefore, assessing gastrointestinal function, at a cellular and functional level, is important to provide optimal enteral nutrition therapy and reduce the gastrointestinal tract's contribution to the inflammatory cascade of critical illness. In this narrative review, we present an overview of biomarker and functional assays for gastrointestinal dysfunction, including epithelial barrier disruption and gastrointestinal dysmotility, that have been considered for critically ill patients.

Bloodstream Infections in Infants and Children With Congenital Heart Disease Undergoing Cardiac Surgery

BACKGROUND

Children with congenital heart disease undergoing cardiac surgery are at risk for laboratory-confirmed bloodstream infections (LCBIs). These infections can lead to morbidity, mortality, and increased health care costs. The role of mucosal barrier injury in causing LCBIs is unknown.

OBJECTIVES

To describe characteristics of LCBIs in patients admitted to cardiac intensive care and step-down units and to assess frequencies of National Healthcare Safety Network infection types and associations with organism classification, patient clinical factors, and infection outcomes.

METHODS

A retrospective cohort analysis using manual electronic medical record data abstraction included children with congenital heart disease who developed an LCBI while receiving inpatient cardiac care between August 2011 and November 2018 at one institution. Demographic, clinical, laboratory, and outcome variables were collected and analyzed with descriptive and inferential statistics.

RESULTS

Eighty-seven patients with congenital heart disease developed 103 LCBIs during the study time frame. The most common causative microorganisms were gram-positive bacteria, including Enterococcus faecalis and Staphylococcus epidermidis. Sixty-three percent of causative organisms were characterized as originating from mucosal barrier injury, although no infections met National Healthcare Safety Network criteria for mucosal barrier injury LCBIs.

CONCLUSIONS

Translocation of bacteria through injured gut mucosa may cause bloodstream infections in children with congenital heart disease. Further investigation is warranted to understand microbiome changes that adversely select pathogenic gut organisms. Preventive care to maintain intact gut function and a healthy microbiome should be explored for this patient population.

Respiratory Microbiome Profile of Pediatric Pulmonary Hypertension Patients Associated With Congenital Heart Disease

BACKGROUND

Pulmonary hypertension (PH) associated with congenital heart disease (CHD) is the most common type of PH in pediatric patients. The airway microbiome profile in CHD-PH patients remains rarely studied.

METHODS

A total of 158 children were recruited for collection of oropharyngeal swabs to sequence the 16S ribosomal RNA (16S rRNA) V3-V4 region of respiratory microbiome, to establish a correlation between these bacterial groups and echocardiography indicators in CHD-PH patients.

RESULTS

Bacterial α- and β-diversity of the airway microbiome indicated a significantly lower richness in the CHD-PH group and compositional differences associated with the specific taxa and their relative abundances in the upper respiratory tract. Principal coordinate analysis showed that the pharynx microbiota composition in the CHD-PH group varied from that in the CHD or control group. The linear discriminant analysis effect size also highlighted an increased presence of Streptococcus and Rothia in pediatric CHD-PH patients. Comparison of microbial composition between pediatric and adult PH patients showed significant differences and separation of microbiota. The correlation between bacterial abundance and transthoracic echocardiography indexes in CHD-associated PH indicated that different groups of microbiomes may be related to different PH grades.

CONCLUSIONS

In summary, our study reported the systematic definition and divergent profile of the upper respiratory tract microbiota in pediatric PH patients, CHD and reference subjects, as well as between pediatric and adult PH patients.

Mapping the early life gut microbiome in neonates with critical congenital heart disease: multiomics insights and implications for host metabolic and immunological health

BACKGROUND

The early life gut microbiome is crucial in maintaining host metabolic and immune homeostasis. Though neonates with critical congenital heart disease (CCHD) are at substantial risks of malnutrition and immune imbalance, the microbial links to CCHD pathophysiology remain poorly understood. In this study, we aimed to investigate the gut microbiome in neonates with CCHD in association with metabolomic traits. Moreover, we explored the clinical implications of the host-microbe interactions in CCHD.

METHODS

Deep metagenomic sequencing and metabolomic profiling of paired fecal samples from 45 neonates with CCHD and 50 healthy controls were performed. The characteristics of gut microbiome were investigated in three dimensions (microbial abundance, functionality, and genetic variation). An in-depth analysis of gut virome was conducted to elucidate the ecological interaction between gut viral and bacterial communities. Correlations between multilevel microbial features and fecal metabolites were determined using integrated association analysis. Finally, we conducted a subgroup analysis to examine whether the interactions between gut microbiota and metabolites could mediate inflammatory responses and poor surgical prognosis.

RESULTS

Gut microbiota dysbiosis was observed in neonates with CCHD, characterized by the depletion of Bifidobacterium and overgrowth of Enterococcus, which was highly correlated with metabolomic perturbations. Genetic variations of Bifidobacterium and Enterococcus orchestrate the metabolomic perturbations in CCHD. A temperate core virome represented by Siphoviridae was identified to be implicated in shaping the gut bacterial composition by modifying microbial adaptation. The overgrowth of Enterococcus was correlated with systemic inflammation and poor surgical prognosis in subgroup analysis. Mediation analysis indicated that the overgrowth of Enterococcus could mediate gut barrier impairment and inflammatory responses in CCHD.

CONCLUSIONS

We demonstrate for the first time that an aberrant gut microbiome associated with metabolomic perturbations is implicated in immune imbalance and adverse clinical outcomes in neonates with CCHD. Our data support the importance of reconstituting optimal gut microbiome in maintaining host metabolic and immunological homeostasis in CCHD. Video Abstract.

Preceding Clinical Events in High-risk, Postoperative, Pediatric Cardiac Patients- A Novel Association With Bacteremia

Objective: Blood stream infections (BSIs) are well described in pediatric cardiac intensive care units (PCICU). We noted that postoperative high-risk patients may develop BSI after a preceding clinical event (PCE). The study aim was to investigate whether high-risk patients who developed bacteremia experienced more PCEs than a similar group of high-risk patients. Design: Retrospective case-control study. Setting: Referral pediatric center. Patients: We enrolled patients who developed bacteremia from March 2010 to November 2019, after undergoing open-heart surgery at a pediatric center. The control group was comprised of case-matched patients with immediate consecutive same surgery. Interventions: None. Measurements: We recorded operative data, common risk factors, postoperative indicators of organ dysfunction, mortality, and PCEs 72 to 24 h before bacteremia emerged. Main results: A total of 200 patients were included (100 with bacteremia and 100 controls). Key demographic and operative parameters were matched. Bacteremia emerged on average on postoperative day 12.8. Skin-associated Gram-positive bacteria were cultured in 10% and Gram-negative bacteria in 84% of the patients. Average central-venous lines (CVL) duration was 9.5 ± 8.4 days. Postoperatively (72 h), indicators of organ dysfunction were significantly worse in patients with bacteremia, with a higher rate of postoperative complications during PCICU length-of-stay (LOS). In the bacteremia group, 72 to 24 h prior to the development of bacteremia, 92 (92%) PCEs were recorded, as compared to 21 (21%) in controls during their entire LOS (odds ratio [OR] 43.3, confidence interval [CI] 18.2-103.1, P < .0001). Conclusions: We propose a 3-hit model demonstrating that high-risk patients undergoing open-heart surgery have significantly higher risk for bacteremia after a PCE.

Clinical Characteristics and Potential Pathogenesis of Cardiac Necrotizing Enterocolitis in Neonates with Congenital Heart Disease: A Narrative Review

Neonates with congenital heart disease (CHD) are at an increased risk of developing necrotizing enterocolitis (NEC), an acute inflammatory intestinal injury most commonly associated with preterm infants. The rarity of this complex disease, termed cardiac NEC, has resulted in a dearth of information on its pathophysiology. However, a higher incidence in term infants, effects on more distal regions of the intestine, and potentially a differential immune response may distinguish cardiac NEC as a distinct condition from the more common preterm, classical NEC. In this review, risk factors, differentiated from those of classical NEC, are discussed according to their potential contribution to the disease process, and a general pathogenesis is postulated for cardiac NEC. Additionally, biomarkers specific to cardiac NEC, clinical outcomes, and strategies for achieving enteral feeds are discussed. Working towards an understanding of the mechanisms underlying cardiac NEC may aid in future diagnosis of the condition and provide potential therapeutic targets.

Immunity and inflammation: the neglected key players in congenital heart disease?

Although more than 90% of children born with congenital heart disease (CHD) survive into adulthood, patients face significantly higher and premature morbidity and mortality. Heart failure as well as non-cardiac comorbidities represent a striking and life-limiting problem with need for new treatment options. Systemic chronic inflammation and immune activation have been identified as crucial drivers of disease causes and progression in various cardiovascular disorders and are promising therapeutic targets. Accumulating evidence indicates an inflammatory state and immune alterations in children and adults with CHD. In this review, we highlight the implications of chronic inflammation, immunity, and immune senescence in CHD. In this context, we summarize the impact of infant open-heart surgery with subsequent thymectomy on the immune system later in life and discuss the potential role of comorbidities and underlying genetic alterations. How an altered immunity and chronic inflammation in CHD influence patient outcomes facing SARS-CoV-2 infection is unclear, but requires special attention, as CHD could represent a population particularly at risk during the COVID-19 pandemic. Concluding remarks address possible clinical implications of immune changes in CHD and consider future immunomodulatory therapies.

Detecting methylation quantitative trait loci using a methylation random field method

DNA methylation may be regulated by genetic variants within a genomic region, referred to as methylation quantitative trait loci (mQTLs). The changes of methylation levels can further lead to alterations of gene expression, and influence the risk of various complex human diseases. Detecting mQTLs may provide insights into the underlying mechanism of how genotypic variations may influence the disease risk. In this article, we propose a methylation random field (MRF) method to detect mQTLs by testing the association between the methylation level of a CpG site and a set of genetic variants within a genomic region. The proposed MRF has two major advantages over existing approaches. First, it uses a beta distribution to characterize the bimodal and interval properties of the methylation trait at a CpG site. Second, it considers multiple common and rare genetic variants within a genomic region to identify mQTLs. Through simulations, we demonstrated that the MRF had improved power over other existing methods in detecting rare variants of relatively large effect, especially when the sample size is small. We further applied our method to a study of congenital heart defects with 83 cardiac tissue samples and identified two mQTL regions, MRPS10 and PSORS1C1, which were colocalized with expression QTL in cardiac tissue. In conclusion, the proposed MRF is a useful tool to identify novel mQTLs, especially for studies with limited sample sizes.

The microbiome’s relationship with congenital heart disease: more than a gut feeling

Patients with congenital heart disease (CHD) are at risk for developing intestinal dysbiosis and intestinal epithelial barrier dysfunction due to abnormal gut perfusion or hypoxemia in the context of low cardiac output or cyanosis. Intestinal dysbiosis may contribute to systemic inflammation thereby worsening clinical outcomes in this patient population. Despite significant advances in the management and survival of patients with CHD, morbidity remains significant and questions have arisen as to the role of the microbiome in the inflammatory process. Intestinal dysbiosis and barrier dysfunction experienced in this patient population are increasingly implicated in critical illness. This review highlights possible CHD-microbiome interactions, illustrates underlying signaling mechanisms, and discusses future directions and therapeutic translation of the basic research.

Impact of uric acid on liver injury and intestinal permeability following resuscitated hemorrhagic shock in rats

BACKGROUND

Multiorgan failure is a consequence of severe ischemia-reperfusion injury after traumatic hemorrhagic shock (HS), a major cause of mortality in trauma patients. Circulating uric acid (UA), released from cell lysis, is known to activate proinflammatory and proapoptotic pathways and has been associated with poor clinical outcomes among critically ill patients. Our group has recently shown a mediator role for UA in kidney and lung injury, but its role in liver and enteric damage after HS remains undefined. Therefore, the objective of this study was to evaluate the role of UA on liver and enteric injury after resuscitated HS.

METHODS

A murine model of resuscitated HS was treated during resuscitation with a recombinant uricase, a urate oxidase enzyme (rasburicase; Sanofi-Aventis, Canada Inc, Laval, Canada), to metabolize and reduce circulating UA. Biochemical analyses (liver enzymes, liver apoptotic, and inflammatory markers) were performed at 24 hours and 72 hours after HS. Physiological testing for enteric permeability and gut bacterial product translocation measurement (plasma endotoxin) were performed 72 hours after HS. In vitro, HT-29 cells were exposed to UA, and the expression of intercellular adhesion proteins (ZO-1, E-cadherin) was measured to evaluate the influence of UA on enteric permeability.

RESULTS

The addition of uricase to resuscitation significantly reduced circulating and liver UA levels after HS. It also prevented HS-induced hepatolysis and liver apoptotic/inflammatory mediators at 24 hours and 72 hours. Hemorrhagic shock-induced enteric hyperpermeability and endotoxemia were prevented with uricase.

CONCLUSIONS

After resuscitated HS, UA is an important mediator in liver and enteric injury. Uric acid represents a therapeutic target to minimize organ damage in polytrauma patients sustaining HS.

Dysbiosis and Intestinal Barrier Dysfunction in Pediatric Congenital Heart Disease Is Exacerbated Following Cardiopulmonary Bypass

There are no data evaluating the microbiome in congenital heart disease following cardiopulmonary bypass. The authors evaluated patients with congenital heart disease undergoing cardiopulmonary bypass and noncardiac patients undergoing surgery without bypass. Patients with congenital heart disease had differences in baseline microbiome compared with control subjects, and this was exacerbated following surgery with bypass. Markers of barrier dysfunction were similar for both groups at baseline, and surgery with bypass induced significant intestinal barrier dysfunction compared with control subjects. This study offers novel evidence of alterations of the microbiome in congenital heart disease and exacerbation along with intestinal barrier dysfunction following cardiopulmonary bypass.

Nutrition and the gut microbiome during critical illness: A new insight of nutritional therapy

Changes in the microbiome in response to environmental influences can affect the overall health. Critical illness is considered one of the major environmental factors that can potentially influence the normal gut homeostasis. It is associated with pathophysiological effects causing damage to the intestinal microbiome. Alteration of intestinal microbial composition during critical illness may subsequently compromise the integrity of the intestinal epithelial barrier and intestinal mucosa absorptive function. Many factors can impact the microbiome of critically ill patients including ischemia, hypoxia and hypotension along with the iatrogenic effects of therapeutic agents and the lack of enteral feeds. Factors related to disease state and medication are inevitable and they are part of the intensive care unit (ICU) exposure. However, a nutritional intervention targeting gut microbiota might have the potential to improve clinical outcomes in the critically ill population given the extensive vascular and lymphatic links between the intestines and other organs. Although nutrition is considered an integral part of the treatment plan of critically ill patients, still the role of nutritional intervention is restricted to improve nitrogen balance. What is dismissed is whether the nutrients we provide are adequate and how they are processed and utilised by the host and the microbiota. Therefore, the goal of nutrition therapy during critical illness should be extended to provide good quality feeds with balanced macronutrient content to feed up the entire body including the microbiota and host cells. The main aim of this review is to examine the current literature on the effect of critical illness on the gut microbiome and to highlight the role of nutrition as a factor affecting the intestinal microbiome-host relationship during critical illness.

Tissue alkaline phosphatase activity and expression in an experimental infant swine model of cardiopulmonary bypass with deep hypothermic circulatory arrest

Background

Infant cardiac surgery with cardiopulmonary bypass results in decreased circulating alkaline phosphatase that is associated with poor postoperative outcomes. Bovine intestinal alkaline phosphatase infusion represents a novel therapy for post-cardiac surgery organ injury. However, the effects of cardiopulmonary bypass and bovine-intestinal alkaline phosphatase infusion on tissue-level alkaline phosphatase activity/expression are unknown.

Methods

Infant pigs (n = 20) underwent cardiopulmonary bypass with deep hypothermic circulatory arrest followed by four hours of intensive care. Seven control animals underwent mechanical ventilation only. Cardiopulmonary bypass/deep hypothermic circulatory arrest animals were given escalating doses of bovine intestinal alkaline phosphatase infusion (0-25 U/kg/hr.; n = 5/dose). Kidney, liver, ileum, jejunum, colon, heart and lung were collected for measurement of tissue alkaline phosphatase activity and mRNA.

Results

Tissue alkaline phosphatase activity varied significantly across organs with the highest levels found in the kidney and small intestine. Cardiopulmonary bypass with deep hypothermic circulatory arrest resulted in decreased kidney alkaline phosphatase activity and increased lung alkaline phosphatase activity, with no significant changes in the other organs. Alkaline phosphatase mRNA expression was increased in both the lung and the ileum. The highest dose of bovine intestinal alkaline phosphatase resulted in increased kidney and liver tissue alkaline phosphatase activity.

Conclusions

Changes in alkaline phosphatase activity after cardiopulmonary bypass with deep hypothermic circulatory arrest and bovine intestinal alkaline phosphatase delivery are tissue specific. Kidneys, lung, and ileal alkaline phosphatase appear most affected by cardiopulmonary bypass with deep hypothermic circulatory arrest and further research is warranted to determine the mechanism and biologic importance of these changes.

Immediate Post-operative Enterocyte Injury, as Determined by Increased Circulating Intestinal Fatty Acid Binding Protein, Is Associated With Subsequent Development of Necrotizing Enterocolitis After Infant Cardiothoracic Surgery

Objectives: 1 Measure serial serum intestinal fatty acid binding protein levels in infants undergoing cardiac surgery with cardiopulmonary bypass to evaluate for evidence of early post-operative enterocyte injury. 2 Determine the association between immediate post-operative circulating intestinal fatty acid binding protein levels and subsequent development of necrotizing enterocolitis. Design: Observational cohort study. Intestinal fatty acid binding protein was measured pre-operatively, at rewarming, and at 6 and 24 h post-operatively. Percent of goal enteral kilocalories on post-operative day 5 and episodes of necrotizing enterocolitis were determined. Multivariable analysis assessed for factors independently associated with clinical feeding outcomes and suspected/definite necrotizing enterocolitis. Setting: Quaternary free-standing children's hospital pediatric cardiac intensive care unit. Patients: 103 infants <120 days of age undergoing cardiothoracic surgery with cardiopulmonary bypass. Interventions: None. Results: Median pre-operative intestinal fatty acid binding protein level was 3.93 ng/ml (range 0.24-51.32). Intestinal fatty acid binding protein levels rose significantly at rewarming (6.35 ng/ml; range 0.54-56.97; p = 0.008), continued to rise slightly by 6 h (6.57 ng/ml; range 0.75-112.04; p = 0.016), then decreased by 24 h (2.79 ng/ml; range 0.03-81.74; p < 0.0001). Sixteen subjects (15.7%) developed modified Bell criteria Stage 1 necrotizing enterocolitis and 9 subjects (8.8%) developed Stage 2 necrotizing enterocolitis. Infants who developed necrotizing enterocolitis demonstrated a significantly higher distribution of intestinal fatty acid binding protein levels at both 6 h (p = 0.005) and 24 h (p = 0.005) post-operatively. On multivariable analysis, intestinal fatty acid binding protein was not associated with percentage of goal enteral kilocalories delivered on post-operative day 5. Higher intestinal fatty acid binding protein was independently associated with subsequent development of suspected/definite necrotizing enterocolitis (4% increase in odds of developing necrotizing enterocolitis for each unit increase in intestinal fatty acid binding protein; p = 0.0015). Conclusions: Intestinal fatty acid binding protein levels rise following infant cardiopulmonary bypass, indicating early post-operative enterocyte injury. Intestinal fatty acid binding protein was not associated with percent of goal enteral nutrition achieved on post-operative day 5, likely due to protocolized feeding advancement based on clinically observable factors. Higher intestinal fatty acid binding protein at 6 h post-operatively was independently associated with subsequent development of necrotizing enterocolitis and may help identify patients at risk for this important complication.

Association between endotoxemia and enterocyte injury and clinical course in patients with gram-positive septic shock: A posthoc analysis of a prospective observational study

Endotoxemia often occurs in patients with gram-positive infections. The possible mechanism is thought to be bacterial translocation after enterocyte hypoperfusion injury. However, the association between endotoxemia and enterocyte injury among patients with gram-positive septic shock has never been assessed. The aim of this study was to evaluate the association between endotoxemia and enterocyte injury in gram-positive septic shock patients and to evaluate the association among endotoxemia, subsequent clinical course, and other related factors.This was a posthoc analysis of a prospective observational study that evaluated the capability of intestinal fatty acid-binding protein (I-FABP), an indicator of enterocyte injury, to predict mortality. Among 57 patients in septic shock, those whose causative microorganisms were gram positive were included. The correlation between endotoxin activity (EA), which indicates endotoxemia, and I-FABP levels upon admission to the intensive care unit (ICU), the clinical course, and other related factors were evaluated.A total of 21 patients were examined. One-third of the patients presented with high EA levels at the time of ICU admission. However, there was no significant correlation between EA and I-FABP levels (Spearman ρ = 0.002, P = .993). Additionally, high EA levels were not associated with abdominal complications after ICU admission or mortality. Similarly, high EA levels were not associated with severity scores, inotropic scores, or lactate levels upon ICU admission, which were previously reported to be factors related to high EA levels.In this posthoc analysis, no correlation was observed between endotoxemia and enterocyte injury among patients in gram-positive septic shock. Additionally, high EA levels were not associated with the clinical course and reported factors related to endotoxemia. Although our results need to be validated in a large prospective cohort study, hypoperfusion enterocyte injury might not be a cause of endotoxemia in these patients. Thus, if there is no correlation between EA and I-FABP levels, other mechanisms that induce high EA levels among patients with gram-positive septic shock should be elucidated.

Alkaline Phosphatase Activity and Endotoxemia After Infant Cardiothoracic Surgery

OBJECTIVE

Infant cardiopulmonary bypass (CPB) increases intestinal permeability leading to endotoxemia. Alkaline phosphatase (AP) reduces endotoxin toxicity in vitro but its effects on endotoxemia in human disease are poorly understood. We assessed the association between serum AP activity and endotoxemia in infants undergoing CPB and determined the effect of ex vivo addition of AP on endotoxemia.

METHODS

Prospective cohort study of 62 infants ≤120 days of age undergoing CPB. AP activity and Endotoxin Activity Assay (EAA) were measured pre-operatively, during rewarming, and 24 h after cardiac intensive care unit admission. In 22 subjects, EAA was measured in pre-operative and rewarming whole blood samples with/without addition of 1,600 U/L of human liver AP.

RESULTS

AP activity decreased during CPB (mean decrease 94.8U/L; P < 0.0001). Median EAA was 0.41 pre-operation, rose to 0.52 (P < 0.05) during rewarming, and remained stably elevated at 24 h. Subjects with low pre-operative AP activity had significantly higher pre-operative (0.47 vs. 0.36; P < 0.05) and rewarming (0.59 vs. 0.43; P < 0.01) EAA with a trend toward higher EAA at 24 h (0.52 vs. 0.45; P = 0.12). Subjects with low rewarming AP activity showed similar differences that did not reach statistical significance. Ex vivo addition of human liver AP decreased pre-operative EAA by 29% (P < 0.001) and rewarming EAA by 51% (P < 0.0001).

CONCLUSION

Endotoxemia is common in infants undergoing CPB. Native AP activity and endotoxemia are inversely related and ex vivo addition of exogenous AP reduces whole blood EAA. Future research should evaluate AP as a therapy to reduce the harmful effects of endotoxemia following infant CPB.

Gut Microbiome in Critical Illness (Review)

Radical changes in the composition, diversity and metabolic activity of gut microbiome in critically ill patients most probably affect adversely the outcome of treatment. Microbiota dysfunction may be a predictor and presumably the main cause of infectious complications and sepsis. Clinicists use objective scales for evaluation of patient condition severity including specific parameters of disorders of organs and systems; however, microbiota function is not considered specific and, hence, not evaluated. Technical capabilities of the recent decade have allowed characterizing the intestinal microbiota and that helped understanding the ongoing processes. The authors have analyzed data about the role of intestinal microbiota as a metabolic 'reactor' during critical states, possible complications related to misbalance of 'harmful' and 'beneficial' bacteria, and examined potential of a targeted therapy aimed directly at correction of intestinal microbiota. Search for papers was carried out using Scopus and Web of Science databases 2001 to 2018 years: (Gut Microbiota) AND (Critically ill OR Intensive care unit), key words taken for the search were: intestinal microbiota, metabolism, sepsis, antibiotics, critically ill patients, multiple organ failure. A number of questions in understanding of the interaction between gut microbiome and host remain open. It is necessary to take into account interference of microbial metabolism while assessing metabolome of patients with sepsis. Among low-molecular compounds found in blood of sepsis patients, special attention should be paid to molecules that can be classified as ‘common metabolites’ of humans and bacteria, for example, degradation products of aromatic compounds, which many-fold rise in blood of septic patients. It is necessary to take into consideration and experimentally model changes in the human internal environment, which occur during radical transformation of microbiome in critically ill patients. Such approach brings in new prospects for objective monitoring of diseases by evaluating metabolic profile at a particular moment of time based on integral indices reflecting the status of microbiome/metabolome system, which will supply new targets for therapeutic intervention in future.

Alkaline Phosphatase in Infant Cardiopulmonary Bypass: Kinetics and Relationship to Organ Injury and Major Cardiovascular Events

OBJECTIVES

To determine the kinetics of alkaline phosphatase (AP) activity and concentration after infant cardiopulmonary bypass, including isoform-specific changes, and to measure the association between postoperative AP activity and major postoperative cardiovascular events, organ injury/dysfunction, and postoperative support requirements STUDY DESIGN: Prospective cohort study of 120 infants ≤120 days of age undergoing cardiopulmonary bypass. AP total and isoform-specific activity was assessed at 6 time points (preoperation, rewarming, 6, 24, 48, and 72 hours postoperation). Low AP activity was defined as ≤80 U/L. AP concentrations and biomarkers of organ injury/dysfunction were collected through 24 hours postoperation. Major cardiovascular events were defined as cardiac arrest, mechanical circulatory support, or death.

RESULTS

AP activity loss occurred primarily during the operation (median decrease 89 U/L; P < .0001) secondary to decreased bone and liver 2 isoforms. Activity declined through 24 hours in 27% of patients. AP activity strongly correlated with serum concentration (r = 0.87-0.91; P < .0001). Persistent low AP activity at 72 hours was associated independently with occurrence of a major cardiac event (OR 5.6; P < .05). Early AP activity was associated independently with subsequent vasoactive-inotropic score (P < .001), peak lactate (P < .0001), peak creatinine (P < .0005), N-terminal pro-brain natriuretic peptide (P < .05), and intestinal fatty acid binding protein (P < .005).

CONCLUSIONS

AP activity decreases during infant cardiopulmonary bypass and may continue to decrease for 24 hours. Activity loss is secondary to decreased bone and liver 2 isoform concentrations. Early low AP activity is associated independently with subsequent postoperative support and organ injury/dysfunction, and persistence of AP activity ≤80 U/L at 72 hours is associated independently with increased odds of major cardiovascular events.

Establishment and evaluation of an experimental rat model for high-altitude intestinal barrier injury

In the present study an experimental high-altitude intestinal barrier injury rat model was established by simulating an acute hypoxia environment, to provide an experimental basis to assess the pathogenesis, prevention and treatment of altitude sickness. A total of 70 healthy male Sprague-Dawley rats were divided into two groups: Control group (group C) and a high-altitude hypoxia group (group H). Following 2 days adaptation, the rats in group H were exposed to a simulated 4,000-m, high-altitude hypoxia environment for 3 days to establish the experimental model. To evaluate the model, bacterial translocation, serum lipopolysaccharide level, pathomorphology, ultrastructure and protein expression in rats were assessed. The results indicate that, compared with group C, the rate of bacterial translocation and the apoptotic index of intestinal epithelial cells were significantly higher in group H (P<0.01). Using a light microscope it was determined that the intestinal mucosa was thinner in group H, there were fewer epithelial cells present and the morphology was irregular. Observations with an electron microscope indicated that the intestinal epithelial cells in group H were injured, the spaces among intestinal villi were wider, the tight junctions among cells were open and lanthanum nitrate granules (from the fixing solution) had diffused into the intestinal mesenchyme. The expression of the tight junction protein occludin was also decreased in group H. Therefore, the methods applied in the present study enabled the establishment of a stable, high-altitude intestinal barrier injury model in rats.

The digestive tract as the origin of systemic inflammation

Failure of gut homeostasis is an important factor in the pathogenesis and progression of systemic inflammation, which can culminate in multiple organ failure and fatality. Pathogenic events in critically ill patients include mesenteric hypoperfusion, dysregulation of gut motility, and failure of the gut barrier with resultant translocation of luminal substrates. This is followed by the exacerbation of local and systemic immune responses. All these events can contribute to pathogenic crosstalk between the gut, circulating cells, and other organs like the liver, pancreas, and lungs. Here we review recent insights into the identity of the cellular and biochemical players from the gut that have key roles in the pathogenic turn of events in these organ systems that derange the systemic inflammatory homeostasis. In particular, we discuss the dangers from within the gastrointestinal tract, including metabolic products from the liver (bile acids), digestive enzymes produced by the pancreas, and inflammatory components of the mesenteric lymph.

Endotoxemia Following Multiple Trauma: Risk Factors and Prognostic Implications

OBJECTIVE

To evaluate the prevalence and time course of systemic endotoxemia following severe multiple trauma, to define its risk factors, and to explore the correlation between post-trauma endotoxemia and organ dysfunction.

DESIGN

Prospective single-center cohort study.

SETTING

Emergency department and ICU of adult tertiary care level I trauma center.

PATIENTS

Forty-eight severely injured (Injury Severity Score ≥ 16) patients, admitted to ICU within 24 hours of injury.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Endotoxemia was not evident on initial presentation, but developed subsequently in 75% of patients, even in the absence of Gram-negative infection. Nonsurviving patients had higher endotoxin levels than survivors on day 1 (endotoxemia, 0.48 vs 0.28; p = 0.048). Shock at admission, or surgery within the first 48 hours after trauma, was associated with higher endotoxin levels and predicted subsequent maximal endotoxemia, after adjusting for other significant covariates. Maximal endotoxemia levels were higher in patients who developed organ dysfunction, reflected in a cumulative Multiple Organ Dysfunction Score greater than 25, and patients with an intermediate endotoxemia level (≥ 0.4) had more cardiovascular dysfunction.

CONCLUSIONS

It is the first study to detect increasing levels of endotoxemia following multiple trauma. Shock and early surgery predict the development of endotoxemia; endotoxemia is particularly associated with cardiovascular dysfunction. However, Gram-negative infections are uncommon in these patients, suggesting that the gastrointestinal tract is the dominant reservoir of endotoxin. Endotoxin may be an appropriate therapeutic target in patients who have sustained severe multiple trauma.

Evaluation of Endotoxemia After Pediatric Cardiac Surgery With the Endotoxin Activity Assay: An Exploratory Prospective Cohort Study

OBJECTIVE

Children with congenital heart diseases undergoing surgery with cardiopulmonary bypass are exposed to a high risk of perioperative endotoxemia. The aim of our study was to prospectively evaluate endotoxin assay activity reference levels during the postoperative phase of infants undergoing cardiac surgery for congenital heart disease and to assess their association with perioperative variables and postoperative infections.

DESIGN

Prospective exploratory single-center cohort study.

SETTING

Tertiary pediatric cardiac ICU.

PATIENTS

Infants undergoing cardiac surgery with cardiopulmonary bypass were enrolled. Exclusion criteria were preoperative suspected or confirmed infection, the need for extracorporeal membrane oxygenation or a ventricular assist device in any perioperative phase, surgery for heart transplantation, and/or urgent surgery.

INTERVENTIONS

Serial measurements of endotoxin assay activity were performed at baseline, pediatric cardiac ICU arrival, postoperative day 1 and 2.

MEASUREMENTS AND MAIN RESULTS

Twenty-five patients were enrolled. Overall, 14 of 25 patients (58%) presented at least one endotoxin assay activity level greater than 0.4 during the study period (normal level is < 0.4). Endotoxin assay activity levels tended to significantly increase from baseline to postoperative day 1 and 2 and from pediatric cardiac ICU arrival to postoperative day 2 (p < 0.0001). Endotoxin assay activity greater than 0.6 predicted Gram-negative infections with a sensitivity of 0.40, a specificity of 0.95, a positive predictive value of 0.66, and a negative predictive value of 0.86. At multivariable regression, endotoxin assay activity on postoperative day 1 resulted independently associated with cardiopulmonary bypass duration, lactate, temperature peak, and vasoactive inotropic score at pediatric cardiac ICU arrival. Children with endotoxin assay activity levels greater than 0.6 (vs all the others) showed a significantly higher median (interquartile) number of ventilation days: 8 (2-39) versus 1.5 (1-3 (p = 0.02).

CONCLUSIONS

This exploratory study showed that endotoxin assay activity levels in infants undergoing cardiopulmonary bypass are frequently above 0.4 and peak 24-48 hours after surgery and appear to be associated with perioperative impaired organ perfusion. Endotoxin assay activity is not useful to predict Gram-negative infections.

Increased adhesion of Plasmodium falciparum infected erythrocytes to ICAM-1 in children with acute intestinal injury

BACKGROUND

Children with severe malaria are at increased risk of invasive bacterial disease particularly infection with enteric gram-negative organisms. These organisms are likely to originate from the gut, however, how and why they breach the intestinal interface in the context of malaria infection remains unclear. One explanation is that accumulation of infected red blood cells (iRBCs) in the intestinal microvasculature contributes to tissue damage and subsequent microbial translocation which can be addressed through investigation of the impact of cytoadhesion in patients with malaria and intestinal damage.

METHODS

Using a static adhesion assay, cytoadhesion of iRBCs was quantified in 48 children with malaria to recombinant proteins constitutively expressed on endothelial cell surfaces. Cytoadhesive phenotypes between children with and without biochemical evidence of intestinal damage [defined as endotoxemia or elevated plasma intestinal fatty acid binding protein (I-FABP)] was compared.

RESULTS

The majority of parasites demonstrated binding to the endothelial receptors CD36 and to a lesser extent to ICAM-1. Reduced adhesion to CD36 but not adhesion to ICAM-1 or rosetting was associated with malarial anaemia (p = 0.004). Increased adhesion of iRBCs to ICAM-1 in children who had evidence of elevated I-FABP (p = 0.022), a marker of intestinal ischaemia was observed. There was no correlation between the presence of endotoxemia and increased adhesion to any of the recombinant proteins.

CONCLUSION

Increased parasite adhesion to ICAM-1 in children with evidence of intestinal ischaemia lends further evidence to a link between the cytoadherence of iRBCs in gut microvasculature and intestinal damage.

Chasing a ghost?--Issues with the determination of circulating levels of endotoxin in human blood

Reliable quantification of bacterial products such as endotoxin is important for the diagnosis of Gram-negative infection and for the monitoring of its treatment. Further, it is important to identify patients with persistent subclinical level of bacterial products in their systemic circulation as data from animal studies also suggest this may be correlated with the onset of metabolic syndrome. In this review, we first aim to describe the principles of the Limulus amoebocyte lysate (LAL) test, an assay that is used to quantify endotoxin, and the various shortcomings that must be addressed before it can become a reliable means of quantifying endotoxin in samples derived from blood. We then review published data regarding endotoxin levels in healthy subjects and those with sepsis, inflammatory bowel disease, liver disorders and metabolic disorders such as obesity and diabetes. We also review the evidence regarding influence of macronutrients in augmenting the levels of systemic endotoxin. The results of this review show that reported mean levels of endotoxin in the systemic circulation of healthy humans and of those with various clinical disorders vary over a wide range. Further, this review shows that a significant proportion of this variation can be related to the method that was used to prepare plasma and serum samples prior to assay and its ability to reduce the effect of various blood borne factors that interfere with the LAL assay.

Nutrition: A Primary Therapy in Pediatric Acute Respiratory Distress Syndrome

Appropriate nutrition is an essential component of intensive care management of children with acute respiratory distress syndrome (ARDS) and is linked to patient outcomes. One out of every two children in the pediatric intensive care unit (PICU) will develop malnutrition or have worsening of baseline malnutrition and present with specific micronutrient deficiencies. Early and adequate enteral nutrition (EN) is associated with improved 60-day survival after pediatric critical illness, and, yet, despite early EN guidelines, critically ill children receive on average only 55% of goal calories by PICU day 10. Inadequate delivery of EN is due to perceived feeding intolerance, reluctance to enterally feed children with hemodynamic instability, and fluid restriction. Underlying each of these factors is large practice variation between providers and across institutions for initiation, advancement, and maintenance of EN. Strategies to improve early initiation and advancement and to maintain delivery of EN are needed to improve morbidity and mortality from pediatric ARDS. Both, over and underfeeding, prolong duration of mechanical ventilation in children and worsen other organ function such that precise calorie goals are needed. The gut is thought to act as a "motor" of organ dysfunction, and emerging data regarding the role of intestinal barrier functions and the intestinal microbiome on organ dysfunction and outcomes of critical illness present exciting opportunities to improve patient outcomes. Nutrition should be considered a primary rather than supportive therapy for pediatric ARDS. Precise nutritional therapies, which are titrated and targeted to preservation of intestinal barrier function, prevention of intestinal dysbiosis, preservation of lean body mass, and blunting of the systemic inflammatory response, offer great potential for improving outcomes of pediatric ARDS. In this review, we examine the current evidence regarding dose, route, and timing of nutrition, current recommendations for provision of nutrition to children with ARDS, and the current literature for immune-modulating diets for pediatric ARDS. We will examine emerging data regarding the role of the intestinal microbiome in modulating the response to critical illness.

Nonpulmonary treatments for pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference

OBJECTIVE

To describe the recommendations from the Pediatric Acute Lung Injury Consensus Conference on nonpulmonary treatments in pediatric acute respiratory distress syndrome.

DESIGN

Consensus conference of experts in pediatric acute lung injury.

METHODS

A panel of 27 experts met over the course of 2 years to develop a taxonomy to define pediatric acute respiratory distress syndrome and to make recommendations regarding treatment and research priorities. The nonpulmonary subgroup comprised three experts. When published data were lacking, a modified Delphi approach emphasizing strong professional agreement was utilized.

RESULTS

The Pediatric Acute Lung Injury Consensus Conference experts developed and voted on a total of 151 recommendations addressing the topics related to pediatric acute respiratory distress syndrome, 30 of which related to nonpulmonary treatment. All 30 recommendations had strong agreement. Patients with pediatric acute respiratory distress syndrome should receive 1) minimal yet effective targeted sedation to facilitate mechanical ventilation; 2) neuromuscular blockade, if sedation alone is inadequate to achieve effective mechanical ventilation; 3) a nutrition plan to facilitate their recovery, maintain their growth, and meet their metabolic needs; 4) goal-directed fluid management to maintain adequate intravascular volume, end-organ perfusion, and optimal delivery of oxygen; and 5) goal-directed RBC transfusion to maintain adequate oxygen delivery. Future clinical trials in pediatric acute respiratory distress syndrome should report sedation, neuromuscular blockade, nutrition, fluid management, and transfusion exposures to allow comparison across studies.

CONCLUSIONS

The Consensus Conference developed pediatric-specific definitions for pediatric acute respiratory distress syndrome and recommendations regarding treatment and future research priorities. These recommendations for nonpulmonary treatment in pediatric acute respiratory distress syndrome are intended to promote optimization and consistency of care for patients with pediatric acute respiratory distress syndrome and identify areas of uncertainty requiring further investigation.

Clinical characteristics associated with postoperative intestinal epithelial barrier dysfunction in children with congenital heart disease

OBJECTIVE

Children with congenital heart disease have loss of intestinal epithelial barrier function, which increases their risk for postoperative sepsis and organ dysfunction. We do not understand how postoperative cardiopulmonary support or the inflammatory response to cardiopulmonary bypass might alter intestinal epithelial barrier function. We examined variation in a panel of plasma biomarkers to reflect intestinal epithelial barrier function (cellular and paracellular) after cardiopulmonary bypass and in response to routine ICU care.

DESIGN

Prospective cohort.

SETTING

University medical center cardiac ICU.

PATIENTS

Twenty children aged between newborn and 18 years undergoing repair or palliation of congenital heart disease with cardiopulmonary bypass.

INTERVENTIONS

We measured baseline and repeated plasma intestinal fatty acid-binding protein, citrulline, claudin 3, and dual sugar permeability testing to reflect intestinal epithelial integrity, epithelial function, paracellular integrity, and paracellular function, respectively. We measured baseline and repeated plasma proinflammatory (interleukin-6, tumor necrosis factor-α, and interferon-γ) and anti-inflammatory (interleukin-4 and interleukin-10) cytokines, known to modulate intestinal epithelial barrier function in murine models of cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

All patients had abnormal baseline intestinal fatty acid-binding protein concentrations (mean, 3,815.5 pg/mL; normal, 41-336 pg/mL). Cytokine response to cardiopulmonary bypass was associated with early, but not late, changes in plasma concentrations of intestinal fatty acid-binding protein 2 and citrulline. Variation in biomarker concentrations over time was associated with aspects of ICU care indicating greater severity of illness: claudin 3, intestinal fatty acid-binding protein 2, and dual sugar permeability test ratio were associated with symptoms of feeding intolerance (p < 0.05), whereas intestinal fatty acid-binding protein was positively associated with vasoactive-inotrope score (p = 0.04). Citrulline was associated with larger arteriovenous oxygen saturation difference (p = 0.04) and had a complex relationship with vasoactive-inotrope score.

CONCLUSIONS

Children undergoing cardiopulmonary bypass for repair or palliation of congenital heart disease are at risk for intestinal injury and often present with evidence for loss of intestinal epithelial integrity preoperatively. Greater severity of illness requiring increased cardiopulmonary support rather than the inflammatory response to cardiopulmonary bypass seems to mediate late postoperative intestinal epithelial barrier function.

A pilot study of Bifidobacterium breve in neonates undergoing surgery for congenital heart disease

Background

Probiotics have currently been widely used in patients undergoing various types of surgeries and improved their clinical outcomes, while data in pediatric cardiac surgery have been lacking. We investigated the safety and effects on the intestinal microbiota of the probiotic Bifidobacterium breve in neonates undergoing surgery for congenital heart disease.

Methods

This pilot, randomized study was performed in a single-center, university hospital-based pediatric intensive care unit (PICU). Twenty-one neonates undergoing surgery for congenital heart disease at >7 days after birth were randomly allocated to two groups: group A received 3 × 10⁹ colony-forming units (CFU)/day of enteral B. breve strain Yakult (BBG-01), which was started 1 week before and terminated 1 week after surgery (n = 10), and group B did not receive BBG-01 (n = 11).

Results

The characteristics of the patients were similar in both groups. The postoperative days until fulfillment of the criteria for discharge from the PICU tended to be fewer in group A (8 [7–8] days) than in group B (9 [8–14] days) (p = 0.10). Likewise, the postoperative days to enteral nutrition or achievement of caloric goal tended to be fewer in group A than in group B. The Bifidobacterium in fecal samples after initiating BBG-01 in group A were significantly higher in number than that in group B. Enterobacteriaceae were significantly fewer in group A than in group B immediately (7.0 [3.9–7.7] vs. 8.5 [8.0–9.1] log₁₀ cells/g) and 1 week (7.7 [7.0–8.1] vs. 9.3 [8.6–9.5] log₁₀ cells/g) after surgery (p < 0.05 for both comparisons). The number of Pseudomonas after 1 week was significantly lower in group A than in group B (p = 0.04). The concentrations of total organic and acetic acids were also significantly higher in group A than in group B. The postoperative course was uncomplicated and all neonates were discharged alive from the PICU.

Conclusions

The perioperative administration of a probiotic to neonates undergoing surgery for congenital heart disease was safe and significantly improved their intestinal environment. The positive effects of this treatment on clinically significant outcomes remain to be investigated.

Synergistic deleterious effect of hypoxemia and hypovolemia on microcirculation in intestinal villi*

OBJECTIVE

To investigate the effect of hypoxemia, hemorrhagic shock, and the association of both of these on intestinal microcirculation (microcirculatory perfusion and leukocytes-endothelium interactions in postcapillary venules), as it can be encountered in hemorrhagic shock following trauma.

DESIGN

Prospective controlled experimental study.

SETTING

University research laboratory.

SUBJECTS

Forty-eight anesthetized and mechanically ventilated Balb/c mice.

INTERVENTION

Mice were randomly assigned to hypoxemia group in which we decreased inspired oxygen fraction during 60 minutes to reach a PaO2 of 40 mm Hg, hemorrhagic shock group in which animals were exsanguinated to a mean arterial pressure level of 40 mm Hg during 30 minutes, hypoxemia-hemorrhagic shock group in which PaO2 was decreased to 40 mm Hg during 60 minutes with exsanguination from the 30th to the 60th minute to a mean arterial pressure level of 40 mm Hg; or control group.

MEASUREMENTS AND MAIN RESULTS

Hypoxemia decreased RBCs velocity in intestinal villi but did not alter the fraction of perfused villi. Hypoxemia also triggered leukocytes adhesion to the venular endothelium. Hemorrhagic shock not only decreased RBCs velocity in villi but also slightly altered the fraction of perfused villi (94% ± 2% in hemorrhagic shock group vs 100% ± 0% in control group, p < 0.005). Furthermore, hemorrhagic shock triggered leukocytes adhesion to the venular endothelium to the same extent as hypoxemia. When hypoxemia was associated to hemorrhagic shock, it decreased villous RBCs velocity in an additive manner and the fraction of perfused villi dropped in a synergistic manner (69% ± 3% in hypoxemia-hemorrhagic shock group vs 94 ± 2 in hemorrhagic shock group, p < 0.005). The association of hypoxemia and hemorrhagic shock did not further amplify leukocytes adhesion to intestinal venules compared with either hypoxemia or hemorrhagic shock alone.

CONCLUSIONS

During hemorrhagic shock, the occurrence of hypoxemia considerably alters villous intestinal perfusion as it decreases the fraction of perfused villi in a synergistic manner, thereby increasing the risk of villous ischemia. The association of hypoxemia and hemorrhagic shock did not amplify leukocytes adhesion to the endothelium further than either hemorrhagic shock or hypoxemia alone did. As hypoxemia frequently occurs simultaneously with hemorrhagic shock in traumatic conditions, it can worsen gut ischemia leading to the exacerbation of multiple organ failure syndrome.

Immunomodulation in sepsis: the role of endotoxin removal by polymyxin B-immobilized cartridge

Severe sepsis results in high morbidity and mortality. Immunomodulation strategies could be an adjunctive therapy to treat sepsis. Endotoxin is a component of gram-negative bacteria and plays an important role in the pathogenesis of septic shock when it is recognized by immune cells. Removal of endotoxin could be an effective adjunctive approach to the management of sepsis. Devices to adsorb endotoxin or inflammatory cytokines have been designed as a strategy to treat severe sepsis, especially sepsis caused by gram-negative bacteria. Polymyxin B-immobilized cartridge has been successfully used to treat patients with sepsis of abdominal origin. Although this cartridge was conceived to adsorb endotoxin, several other immunological mechanisms have been elucidated, and this device has also yielded promising results in patients with nonseptic respiratory failure. In this paper, we summarize the immune modulation actions of Polymyxin B-immobilized cartridge to explore its potential usefulness beyond endotoxin elimination.

Endotoxaemia is common in children with Plasmodium falciparum malaria

Background

Children presenting to hospital with recent or current Plasmodium falciparum malaria are at increased the risk of invasive bacterial disease, largely enteric gram-negative organisms (ENGO), which is associated with increased mortality and recurrent morbidity. Although incompletely understood, the most likely source of EGNO is the bowel. We hypothesised that as a result of impaired gut-barrier function endotoxin (lipopolysaccharide), present in the cell-wall of EGNO and in substantial quantities in the gut, is translocated into the bloodstream, and contributes to the pathophysiology of children with severe malaria.

Methods

We conducted a prospective study in 257 children presenting with malaria to two hospitals in Kenya and Uganda. We analysed the clinical presentation, endotoxin and cytokine concentration.

Results

Endotoxaemia (endotoxin activity ≥0.4 EAA Units) was observed in 71 (27.6%) children but its presence was independent of both disease severity and outcome. Endotoxaemia was more frequent in children with severe anaemia but not specifically associated with other complications of malaria. Endotoxaemia was associated with a depressed inflammatory and anti-inflammatory cytokine response. Plasma endotoxin levels in severe malaria negatively correlated with IL6, IL10 and TGFβ (Spearman rho: TNFα: r=−0.122, p=0.121; IL6: r=−0.330, p<0.0001; IL10: r=−0.461, p<0.0001; TGFβ: r=−0.173, p<0.027).

Conclusions

Endotoxaemia is common in malaria and results in temporary immune paralysis, similar to that observed in patients with sepsis and experimentally-induced endotoxaemia. Intense sequestration of P. falciparum-infected erythrocytes within the endothelial bed of the gut has been observed in pathological studies and may lead to gut-barrier dysfuction. The association of endotoxaemia with the anaemia phenotype implies that it may contribute to the dyserythropoesis accompanying malaria through inflammation. Both of these factors feasibly underpin the susceptibility to EGNO co-infection. Further research is required to investigate this initial finding, with a view to future treatment trials targeting mechanism and appropriate antimicrobial treatment.

Bench-to-bedside review: Clinical experience with the endotoxin activity assay

Endotoxin detection in human patients has been a difficult challenge, in part due to the fact that the conserved active portion of the molecule (lipid A) is a relatively small epitope only amenable to binding by a single ligand at any one instance and low levels (pg/ml) are capable of stimulating the immune system. The endotoxin activity assay, a bioassay based on neutrophil activation by complement opsonized immune complexes of lipopolysaccharide (LPS), has allowed the specific detection of the lipid A epitope of LPS in a rapid whole blood assay format. This review summarizes diagnostic studies utilizing the endotoxin activity assay in a variety of hospital patient populations in whom endotoxin is postulated to play a significant role in disease etiology. These include ICU patients at risk of developing 'sepsis syndrome', abdominal and cardiovascular surgery patients and patients with serious traumatic injury. Significant features of these studies include the high negative predictive value of the assay (98.6%) for rule out of Gram-negative infection, ability to risk stratify patients progressing to severe sepsis (odds ratio 3.0) and evidence of LPS release in patients with gut hypoperfusion. Preliminary studies have successfully combined the assay with anti-LPS removal strategies to prospectively identify patients who might benefit from this therapy with early evidence of clinical benefit.

Gut microbial translocation in critically ill children and effects of supplementation with pre- and pro biotics

Bacterial translocation as a direct cause of sepsis is an attractive hypothesis that presupposes that in specific situations bacteria cross the intestinal barrier, enter the systemic circulation, and cause a systemic inflammatory response syndrome. Critically ill children are at increased risk for bacterial translocation, particularly in the early postnatal age. Predisposing factors include intestinal obstruction, obstructive jaundice, intra-abdominal hypertension, intestinal ischemia/reperfusion injury and secondary ileus, and immaturity of the intestinal barrier per se. Despite good evidence from experimental studies to support the theory of bacterial translocation as a cause of sepsis, there is little evidence in human studies to confirm that translocation is directly correlated to bloodstream infections in critically ill children. This paper provides an overview of the gut microflora and its significance, a focus on the mechanisms employed by bacteria to gain access to the systemic circulation, and how critical illness creates a hostile environment in the gut and alters the microflora favoring the growth of pathogens that promote bacterial translocation. It also covers treatment with pre- and pro biotics during critical illness to restore the balance of microbial communities in a beneficial way with positive effects on intestinal permeability and bacterial translocation.

Markers of intestinal injury are associated with endotoxemia in successfully resuscitated patients

AIMS

Gut dysfunction is suspected to play a major role in the pathophysiology of post-resuscitation disease through an increase in intestinal permeability and endotoxin release. However this dysfunction often remains occult and is poorly investigated. The aim of this pilot study was to explore intestinal failure biomarkers in post-cardiac arrest patients and to correlate them with endotoxemia.

METHODS

Following resuscitation after cardiac arrest, 21 patients were prospectively studied. Urinary intestinal fatty acid-binding protein (IFABP), which marks intestinal permeability, plasma citrulline, which reflects the functional enterocyte mass, and whole blood endotoxin were measured at admission, days 1-3 and 6. We explored the kinetics of release and the relationship between IFABP, citrulline and endotoxin values.

RESULTS

IFABP was extremely high at admission and normalized at D3 (6668 pg/mL vs 39 pg/mL, p=0.01). Lowest median of citrulline (N=20-40 μmol/L) was attained at D2 (11 μmol/L at D2 vs 24 μmol/L at admission, p=0.01) and tended to normalize at D6 (21 μmol/L). During ICU stay, 86% of patients presented a detectable endotoxemia. Highest endotoxin level was positively correlated with highest IFABP level (R(2)=0.31, p=0.01) and was inversely correlated with lowest plasma citrulline levels (R(2)=0.55, p<0.001). Endotoxin levels increased between admission and D2 in patients with post-resuscitation shock, whereas it decreases in patients with no shock (median +0.33 EU vs -0.19 EU, p=0.03). Highest endotoxin level was positively correlated with D3 SOFA score (R(2)=0.45, p=0.004).

CONCLUSION

Biomarkers of intestinal injury are altered after cardiac arrest and are associated with endotoxemia. This could worsen post-resuscitation shock and organ failure.